As of 1 January 2005
The first part of this project is to construct a running water cooled 50-ohm termination for testing the amplifier. The design is similar to Bird's economy terminations. The water source is any garden/lawn spigot. The heated discharge water can be used to water the grass. In addition to the load resistor, this termination will incorporate a 1:1000 voltage-divider to allow measuring the peak RF potential across the 50-ohm termination with a calibrated oscilloscope.
The major components are the 50-ohm, 500w (in air) resistor, the ABS pipe/fittings for the waterjacket and water-in.out connections, and a water-tight Type-C female chassis connector.The major components. Construction steps:pic01. pic02. pic03. pic04. pic05. pic06 pic07. pic08. pic09. pic10, pic11, pic12,
-- Chassis layout, RF deck. width, pic12; depth, pic13.
-- Plywood box (power supply unit):
P.S. Unit Design Details. A FWD / C-filter was chosen because the advantage of using a FWB / resonant-choke filter would be offset by the requirement for a heavier HV transformer, a choke, and a resonating capacitor. Modern, low-ESR 105ºC, electrolytic capacitors were chosen for the filter because they are more compact and lighter than equivalent (93uF, 4950WV) oil-filled units. Another advantage of using this type of capacitor, is being able to use reliable MOF resistors (Matsushita 100k, 3w, 500v) for the equalizers--bleeders. The main advantage of a longiah bleed-down time is that the 5 or so minutes needed can be spent quenching one's thirst with an "807". Had I used oil-filled filter capacitors, I would have needed to mount the 22, 100k-ohm, 3w seriesed resistors on a seperate perfboard.
After pricing HV connectors, I opted for using ordinary banana plugs and sockets, mounted on insulating plates to carry the 9900V. The HV wire (yellow and white in the photos) is silicone-rubber insulated. We tested it at 20kV, although I have no idea what the mfg's rating is.
Power.Supply Unit Construction Pictures: pic14, sides & back; pic15, the 1700rpm blower and its mounting bracket; pic 16,the inlet air filter screen; pic 17, gluing electrolytic filter capacitors to the ABS base with silicone-rubber adhesive pic 18, filter C-bank showing the first pair of capacitors wired in parallel with their 100k-ohm, 3w equalizer-R; pic19, wiring a filter C-bank:pic20, measuring rectifier PIV; pic22, soldering rectifiers; pic23, Solder side of FWD / FWB rectifier board plus bending jig for the 56 rectifiers; pic24, component side of rectifier board. Testing the FWD / FWB rectifier circuit: The orange box is a x1000 V-multiplier for the DVM. 2800Vrms tap, FWB: pic 25. /// FWD, 2800Vrms tap, pic 26. FWD / FWB HV relay, pic27.
- to be continued -